U.S. patent number 4,036,661 [Application Number 05/331,424] was granted by the patent office on 1977-07-19 for asphalt mineral aggregate compositions containing silanes as adhesion promoters.
This patent grant is currently assigned to Chevron Research Company. Invention is credited to Peter E. Graf, Robert J. Schmidt, deceased.
United States Patent |
4,036,661 |
Schmidt, deceased , et
al. |
July 19, 1977 |
Asphalt mineral aggregate compositions containing silanes as
adhesion promoters
Abstract
Surfacing compositions are provided which comprise a mixture of
mineral aggregate, asphalt and a silane of the formula: wherein (a)
X represents halogen or alkoxy, (b) R.sup.a represents alkylene and
(c) R.sup.b represents amino, aminoalkylene amino, gamma-glycidoxy,
hydrocarbyl, acyloxy or mercapto.
Inventors: |
Schmidt, deceased; Robert J.
(late of El Cerrito, CA), Graf; Peter E. (Orinda, CA) |
Assignee: |
Chevron Research Company (San
Francisco, CA)
|
Family
ID: |
23293906 |
Appl.
No.: |
05/331,424 |
Filed: |
February 12, 1973 |
Current U.S.
Class: |
106/284.2;
106/284.06; 106/277; 106/284.4 |
Current CPC
Class: |
C08K
5/54 (20130101); C08K 5/54 (20130101); C08L
95/00 (20130101) |
Current International
Class: |
C08L
95/00 (20060101); C08L 095/00 (); C09D
003/24 () |
Field of
Search: |
;106/273N,277,287SB,281N
;260/448.2,448.8 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Schofer; Joseph L.
Assistant Examiner: Lilling; Herbert J.
Attorney, Agent or Firm: Tonkin; C. J. Brooks; J. T.
Claims
We claim:
1. A surfacing composition comprising (A) 100 parts by weight of a
mineral aggregate, (B) 3 to 20 parts by weight of an asphalt and
(C) from 0.0001 to 0.10 parts by weight of a silane of the
formula:
wherein
1. X represents halogen or alkoxy,
2. R.sup.a represents alkylene, and
3. R.sup.b represents amino or aminoalkylene amino.
2. A composition of claim 1 wherein:
a. X represents halogen or alkoxy containing 1 to 4 carbon
atoms,
b. R.sup.a represents an alkylene containing from 2 to 4 carbon
atoms, and
c. R.sup.b represents amino or aminoalkyleneamino containing 1 to 3
carbon atoms.
3. A composition of claim 2 wherein the components of said
composition are intimately mixed.
4. A composition of claim 3 wherein:
a. X represents chlorine, methoxy or ethoxy,
b. R.sup.a represents trimethylene, and
c. R.sup.b represents amino or aminoethylene amino.
5. A surfacing composition of claim 3 wherein said silane is
aminoethyleneaminopropyl trimethoxy silane.
6. A composition comprising an asphalt and about 0.001 to about 1.0
percent weight of a silane of the formula:
wherein
1. X represents halogen or alkoxy,
2. R.sup.a represents alkylene, and
3. R.sup.b represents amino or aminoalkylene amino.
7. A composition of claim 6 wherein:
a. X represents halogen or alkoxy containing 1 to 4 carbon
atoms,
b. R.sup.a represents an alkylene containing from 2 to 4 carbon
atoms, and
c. R.sup.b represents amino or aminoalkylene amino containing 1 to
3 carbon atoms.
8. A composition of claim 7 wherein:
a. X represents chlorine, methoxy or ethoxy,
b. R.sup.a represents trimethylene, and
c. R.sup.b represents amino or aminoethylene amino.
9. An asphalt composition having a high adhesion strength,
comprising road-paving asphalt having mixed therein from 0.0005 to
3.33% by weight, based on the amount of asphalt, of an aminoalkyl
polyalkoxysilane having the formula:
wherein
1. X represents alkoxy,
2. R.sup.a represents alkylene, and
3. R.sup.b represents amino or aminoalkylene amino.
10. An asphalt composition according to claim 9, in which said
aminoalkyl polyalkoxysilane is selected from the group consisting
of .beta.-aminoethyl-.gamma.-aminopropyl trimethoxysilane, and
.gamma.-aminopropyl triethoxysilane.
11. A method for preparing asphalt having a high adhesion strength,
which comprises incorporating in roadpaving asphalt from 0.0005 to
3.33 percent by weight, based on the amount of asphalt, of an
aminoalkyl polyalkoxysilane having the formula:
wherein
1. X represents alkoxy,
2. R.sup.a represents alkylene, and
3. R.sup.b represents amino or aminoalkylene amino.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to asphalt surfacing compositions and
more particularly to compositions for use in paving construction,
which compositions have improved adhesion of the asphalt binder to
the mineral aggregate. The improved adhesion is obtained by
including in the surfacing composition a silane as described herein
below. The silane may be added either to the asphalt or to the
mineral aggregate prior to mixing. The compositions show a
surprising increase in the adhesion of the binder to the mineral
aggregate even when completely immersed in water for extended
periods.
2. Description of the Prior Art
A wide variety of silicon compounds including silanes have been
used for the impregnation and surface treatment of glass fibers to
promote the adhesion of various organic resins such as the
polyester resins, epoxide resins or phenol formaldehyde resins and
for the surface treatment of textiles, leathers, ceramics and glass
materials.
It has been found that the adhesion of asphalt to siliceous
aggregates could be markedly improved by first treating the
aggregate with vapors of a mixture of methylchlorosilanes. However,
this exotic method of application of the silanes to the aggregate
is not practical in large scale applications. Sanderson, F. C.,
"Methylchlorosilanes as Anti-stripping Agents". Proceedings,
Highway Research Board, 31, 288 (1952).
U.S. Pat. No. 2,570,185 (106-273) issued Oct. 9, 1951 discloses
that the reaction product of aminoalkoxysilanes and high molecular
weight aliphatic primary amines containing at least 6 carbon atoms
may be added to asphalt to improve the coating properties and
anti-stripping properties of the asphalt. The only example of a
silane shown in this reference is di-t-butoxy-diamino silane. U.S.
Pat. No. 2,985,678 (260-448.8) issued May 23, 1961 discloses that
higher alkyl or aryl radicals in silicon compounds progressively
lower the stability of the compounds. However, the tertiary butyl
radical is shown to increase the stability of the silicon
compounds, even in silicon compounds which contain long chain alkyl
such as lauryl group.
German Pat. No. 800,685 teaches silanes as asphalt adhesion agents.
The useful silanes are said to be of the formula SiR.sub.m X.sub.n
wherein X represents a halogen or an alkoxy, R represents an
organic residue and m and n represent integers of from 1 to 3.
Specific examples of R include methyl, phenyl and
2-chloroethylene.
The patent literature, particularly class 106, subclasses 273 and
277 is replete with attempts to improve the adhesion of asphalt
binders to mineral aggregate. The patent literature referring to
silicon compound chemistry continually is concerned with the
thermal stability of silicon compounds. Thus it may be seen it is
highly desirable compounds of any type be found which not only
promote the adhesion of asphalt to mineral aggregate but also
remain stable over a wide temperatue range and for an extended
period. In addition to this it is highly desirable that the
adhesion promoters be capable of being used without exotic
application methods. Preferably the promoter should be susceptible
of introduction into the asphalt in the molten state or application
to the mineral aggregate prior to mixing with the asphalt or
both.
SUMMARY OF THE INVENTION
It is now found that particular trihalo and trialkoxy silanes are
useful for promoting the adhesion of asphalt to mineral aggregate.
These silanes are susceptible of introduction into asphalt-mineral
aggregate surfacing compositions at any stage of their preparation.
Furthermore, these silanes increase the quantity of asphalt
retained on the aggregate after severe hot water stripping tests.
Typically, a ten to twentyfold increase in retained asphalt is
found compared to the results with conventional anti-stripping
agents.
In brief, the surfacing compositions of the invention comprise (A)
a mineral aggregate, (B) an asphalt, and (C) a trihalo or trialkoxy
silane of the formula set forth below.
DETAILED DESCRIPTION OF THE INVENTION
The surfacing compositions of this invention in which the adherence
of the asphalt to the mineral aggregate is substantially increased
comprise: (A) 100 parts by weight of a mineral aggregate; (B) from
3 to 20 parts by weight of an asphalt and (C) from 0.0001 to 0.10
part by weight of a silane of the formula:
the Mineral Aggregate
The particular mineral aggregates used to form the surfacing
compositions of this invention are not critical. They may be
siliceous in nature, e.g. granite and the like or calcareous in
nature; e.g., limestone and the like or mixtures thereof.
The Asphalt
A wide variety of asphalts may be used to prepare the surfacing
compositions of the subject invention. In general, any paving grade
asphaltic binder satisfactory for preparing paving compositions is
contemplated as being useful in the subject invention. Paving grade
asphalts can have a wide range of penetration values ranging from
as low as 30 or 40 dmm for the harder asphalts to 200 to 300 dmm at
77.degree. F. (100 g, sec.) for the softer asphalts. The most
widely used paving asphalts generally have a penetration at
77.degree. F. of about 50-60 or 60-70 dmm.
The Adhesion Promoters
The adhesion promoters used in the preparation of the sufacing
compositions of this invention are the trihalo, or trialkoxy
silanes of formula I above.
In formula I above:
a. X represents halogen, e.g., flourine, chlorine, bromine and the
like, preferably chlorine, or alkoxy containing 1 to 4 carbon
atoms, e.g., methoxy, ethoxy, propoxy, isopropoxy, butoxy,
isobutoxy, sec-butoxy, tert-butoxy;
b. R.sup.a represents alkylene preferably containing 2 to 4 carbon
atoms, e.g., ethylene, trimethylene, methylethylene, alpha-methyl
trimethylene, beta-methyl trimethylene, tetramethylene, and the
like;
c. R.sup.b represents amino; aminoalkylene amino, preferably
containing 1 to 3 carbon atoms, e.g., amino methylene amino,
aminoethylene amino, aminotrimethylene amino, aminoethylethylene
amino; gamma-glycidoxy, hydrocarbyl, preferably containing from 12
to 19 carbon atoms, e.g., dodecyl, tridecyl, tetradecyl,
pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl, and the
like; acyloxy, preferably containing 2 to 4 carbon atoms, e.g.,
ethanoyloxy, propanoyloxy, butanoyloxy, 2-butenoyloxy, and the
like; or mercapto.
The silanes are present in the surfacing composition in an amount
effective to substantially increase the amount of asphalt remaining
on the aggregate after the water immersion test described below. By
substantially, is meant at least 10 percent and preferably at least
50 percent relative to the amount of asphalt coating aggregate in
surfacing compositions not containing an adhesion promoter. In
general, the amount of silanes necessary to substantially increase
the asphalt coating the aggregate after the stripping test will
range from about 0.0001 part to about 0.10 part by weight per 100
parts of mineral aggregate present in the surfacing composition.
Preferably, the silanes are present in amounts ranging from about
0.0005 to about 0.05 part by weight per 100 parts of mineral
aggregate.
The silanes can be introduced into the surfacing compositions in a
variety of ways during the manufacture of the surfacing
compositions.
The silanes can be added to molten asphalt prior to mixing with the
aggregate. When added in this manner the concentration of the
silane in the asphalt must be adjusted such that the proper
concentration is obtained when the asphalt is mixed with the
aggregate. Typically, the silanes will be present in the asphalt in
from about 0.001 to about 1.0 percent weight preferably 0.005 to
about 0.5 percent weight.
Another method is to pretreat the aggregate with the silane prior
to addition of the emulsion. Since very small quantities of silane
are used relative to the aggregate, the silane is most conveniently
added to the aggregate in the form of a solution. Suitable solvents
include water and most of the inert liquid hydrocarbon solvents
which are compatible and nonreactive with the silane. Examples
include benzene, toluene, xylene, pentane and the like. There are a
number of limitations attendant to the pretreatment of the
aggregate with a hydrocarbon solution of the silane. These include
the requirement that the aggregate be moderately dry during silane
application. Second, the presence of the volatile solvent
represents both an air pollution problem and a fire hazard. For
greatest economy and ease of handling, the preferred solvent for
silane pretreatment of the aggregate is water. Most conveniently,
the silane is dissolved in the water and the solution applied to
the aggregate prior to drying.
Other Materials
In addition to the above mentioned ingredients of the surfacing
compositions of the invention, a number of other materials can be
present. These can include materials which affect the physical
properties of the asphalt in the finished surface composition, such
as additives which improve the high and low temperature
characteristics of the asphalt.
In general, any additives which have been used in the prior art to
improve the resulting surfacing compositions and which are
compatible with the silanes can be added to the surfacing
compositions of this invention. The selection and use of these
additives is not a part of this invention and such matters are well
within the purvue of those skilled in the art. The testing of the
compatibility of proposed additives with the silanes used in this
invention is straightforward and easily conducted. Small samples
can be prepared and tested by the water immersion test described
below as well as other standard tests used to determine the
properties of asphaltic type surfacing compositions.
The Surfacing Compositions
The surfacing compositions of the invention are prepared by mixing
together, in the proportions indicated above, the mineral
aggregate, the asphalt, and the silane. For best results, the
components are preferably intimately mixed to obtain a uniform
distribution of the asphalt and silane onto the surface of the
mineral aggregate.
TEST OF ASPHALT-AGGREGATE ADHESION
General Procedure for Sample Preparation and Water Immersion
Testing (Stripping Resistance)
Surfacing compositions are prepared by mixing 5 parts of a paving
asphalt with 100 parts of aggregate. Prior to mixing, both the
asphalt and aggregate are heated to 325.degree. F. Unless otherwise
indicated, the mixture is cured for 15 minutes at 275.degree. F.,
redispersed to assure completeness of coating, and allowed to cool
to room temperature. Following the prescribed cure, the samples are
subjected to water immersion. Typically, a variety of immersion
conditions are investigated. These can include a short exposure in
boiling water, typically one or two minutes; longer exposures at
room temperature, and 140.degree. F. and 180.degree. F. for 1, 4
and 8 days and 3 months. The percent coating remaining on the
aggregate at completion of the water immersion test is rated
visually on a scale of 0-100%. For purposes of quality control one
or more of the above conditions are often omitted and only the
boiling water test is conducted.
In the following examples, all parts are parts by weight unless
otherwise expressed.
EXAMPLE I
Effect of Silane Concentration
A paving grade asphalt (50/60 penetration at 77.degree. F.) was
prepared to contain from 0.002% W to 1.0% W of
3-{N-(2-aminoethyl)amino}propyltrimethoxysilane. This asphalt (5
parts) was mixed with a Bristol silica stone (100 parts) graded
such that 100% passes a 3/8 inch U.S. standard sieve and 100% is
retained on an 1/4 inch U.S. standard sieve. The mixture then
contains 1 ppm to 500 ppm relative to the aggregate. The mixtures
were cured for 15 minutes either at 275.degree. F. or 325.degree.
F. and then allowed to cool to room temperature after which water
immersion tests were made. The results are shown in Table I.
TABLE I ______________________________________ Silane Concentration
Immersion Cure Relative to Aggregate, ppm Time Temp Temp 0 1 5 50
250 500 ______________________________________ 2 min Boiling 275 25
-- 90 100 100 100 Water 325 30 95 100 100 100 100 275 10 --
85.sup.a 100 100 100 1 day 140.degree. F. 325 10 -- 95 100 100 100
275 5 -- 80 95 95 100 4 days 140.degree. F. 325 10 90 95 100 100
100 140.degree. F. 275 5 -- 85 95 95 100 8 days 140.degree. F. 325
5 80 95 100 100 100 275 5 -- 70 100 100 100 1 day 180.degree. F.
325 5 -- 80.sup.a 100 100 100 275 5 -- -- 80.sup.b 80.sup.b -- 4
days 180.degree. F. 325 5 30 50 85.sup.b 100.sup.b 100.sup.b 275 2
-- 20 30.sup.b 30.sup.b 30.sup.b 8 days 180.degree. F. 325 2 20
40.sup.b 75.sup.b 90 100 ______________________________________
.sup.a Coating thins rather strips off .sup.b Rocks retain black
coating but extremely thin in places due to flo of asphalt, i.e.,
adhesive strength is greater than cohesive strength
As little as 1 ppm silane relative to the aggregate was effective
in giving a tenfold increase in asphalt retained on the stone
compared to results obtained without silane, even under the
conditions of the very severe 8-day, 180.degree. F. water immersion
test. It may also be noticed that in most cases, higher cure
temperatures gave better results.
EXAMPLE II
Effect of Silane Concentration and Long-Term Curing of Mixes at
Elevated Temperatures
Bristol silica stone graded as in Example I was pretreated with
benzene solutions of the same silane and dried to leave 8, 20 and
40 ppm silane on the stone. Mixes of the pretreated stone and the
same asphalt were prepared. They were cured 14 minutes at
275.degree. F., 18 hours at 200.degree. F. and then 3 hours as
indicated in Table II after which water immersion tests were made.
The results are also shown in Table II.
TABLE II
__________________________________________________________________________
PERCENT COATING AFTER IMMERSION AS A FUNCTION OF SILANE
CONCENTRATION AND CURING TEMPERATURE
__________________________________________________________________________
Immersion Temperature 70.degree. F. 140.degree. F. 180.degree. F.
Boiling Water Immersion Cure Concentration Silane - Relative to
Aggregate, ppm Time Temp.,.degree. F. 0 8 20 40 0 8 20 40 0 8 20 40
0 8 20 40
__________________________________________________________________________
325 100.sup.a 100.sup.a 100.sup.a 100.sup.a 95 95 95 90.sup.b
95.sup.c 95.sup.c 95.sup.c 95.sup.c 100 100 100 100 1-Day 275
100.sup.a 100.sup.a 100.sup.a 100.sup.a 20 100 100 100 5.sup.c
95.sup.c 95.sup.c 95.sup.c 70 100 100 100 200 100.sup.a 100.sup.a
100.sup.a 100.sup.a 5 95.sup.b 95.sup.b 98.sup.b 5 85 90 90
20.sup.d 95 95 95 325 100.sup. e 100.sup.e 100.sup.e 100.sup.e
95.sup.f 100 100 95 80.sup.g 100.sup.g 100.sup.g 100.sup.g 3-Day
275 100.sup.e 100.sup.e 100.sup.e 100.sup.e 15 95 95 95 5 90 95 95
200 100.sup.e 100.sup.e 100.sup.e 100.sup.e 5 95 90 95 5 80 90 95
__________________________________________________________________________
.sup.a Coating slightly wrinkled but coherent .sup.b Many small
collapsed blisters; coating still continuous .sup.c Dull, slightly
waxy coating; a few collapsed (but coherent) "blisters"- .sup.d A
few collapsed, closed "blisters"; coating continuous .sup.e Slight
wrinkling but glossy, coherent black surface .sup.f Slight waxy
coating .sup.g Very dull, waxy, brownish cast; scratched easily to
black, coheren coating
In most cases, the silane markedly increased the amount of asphalt
remaining on the treated aggregate relative to the untreated
aggregate. Little or no difference was expected or observed at the
70.degree. F. immersion temperature. Under these mild conditions,
differences would be expected only after longer immersion
periods.
EXAMPLE III
Effect of Silane on Long-Term Immersion
Asphalt-aggregate mixes were prepared as in Example I such that
they contained 0, 1, 5 and 50 ppm silane relative to the aggregate.
After three months' immersion at 140.degree. F., coating retentions
of about 0, 50, 80 and 100 percent, respectively, were observed.
Samples immersed at room temperature for 3 months retained only
80-90% of their coating without the silane. Samples in which the
aggregate was pretreated with 8 ppm silane retained more than 90%
of their coating.
EXAMPLE IV
High Temperature Stability of Silane Preblended in Asphalt
Asphalts containing 0.1, 0.5 and 1.0% W silane of Example I were
prepared and stored at 275.degree. F. and 325.degree. F. Portions
of the treated asphalt stored at these temperatures for 1 to 8 days
were used to prepared mixes with silica stone as described in the
general test description above. Immersion tests in boiling water
and at 140.degree. F. for one and four days were made. The results
are shown in Table IV.
TABLE IV
__________________________________________________________________________
Silane Concentration Relative to Aggregate, ppm Asphalt 0 50
__________________________________________________________________________
Storage Additive-Asphalt Storge Period, Days
__________________________________________________________________________
Time Temp Temp 1 2 3 4 8 1 2 3 4 8 1
__________________________________________________________________________
2 Min Boil- Room ing Temp 5 -- 10 10 15 100 -- 100 -- 100 100 Water
275 10 15 10 10 15 95 60 20 30 80 100 325 15 15 10 10 15 80 60 40
30 85 100 1 Day 140.degree. F. R.T. 5 -- 10 -- 5 95 -- 100 -- 100
100 275 5 5 10 5 5 90 40 25 20 95 100 325 5 10 10 5 5 50 20 20 20
90 95 4 Days 140.degree. F. 275 2 5 325 2 5
__________________________________________________________________________
Silane Concentration Relative to Aggregate, ppm Asphalt 250 500
__________________________________________________________________________
Storage Additive-Asphalt Storage Period, Days
__________________________________________________________________________
Time Temp Temp 2 3 4 8 1 2 3 4 8
__________________________________________________________________________
2 Min Boil- Room ing Temp -- 100 -- 100 100 -- 100 -- 100 Water 275
95 95 100 90 100 100 100 100 85 325 90 90 70 95 100 95 95 95 95 1
Day 140.degree. F. R.T. -- 100 -- 100 100 -- 100 -- 100 275 100 95
95 80 100 75 10 100 100 325 90 85 90 100 100 95 100 95 100 4 Days
140.degree. F. 275 95 100 325 50 100
__________________________________________________________________________
EXAMPLE V
A variety of silanes were tested for their effectiveness as
adhesion promoters. The silane was added to the paving grade
asphalt used in Example I at treatment levels of 0.02, 0.1 and 0.5%
W. Five parts of the treated asphalt was mixed with 100 parts of
the silica aggregate of Example I, cured, and water immersion
tested according to the general procedure described above. The
silanes tested, treatment levels relative to the aggregate,
immersion conditions and results are shown in Table V.
TABLE V
__________________________________________________________________________
EFFECTS OF VARIOUS SILANE ADHESION AGENTS ON PERCENT ASPHALT
COATING RETAINED ON SILICA AGGREGATE AFTER DIFFERENT IMMERSION
PERIODS IN WATER
__________________________________________________________________________
Test Immersion Conditions Additive Concentration Relative to
Boiling Water 140.degree. F./1 Day 140.degree. F./6 140.degree.
F./3 Months No. Aggregate, ppm 250 50 10 250 50 10 250 50 10 250 50
10
__________________________________________________________________________
1 3-{N-(2-aminoethyl)amino}propyl- 100 100 100 100 100 100 100 100
100 100 100 100 trimethoxysilane 2
gamma-glycidoxypropyltrimethoxysilane 100 100 100 100 -- 100 100
100 100 100 100 100 3 Octadecyltrichlorosilane 100 100 100 90 70 90
90 50 50 80 50 30 4 gamma-Aminopropyltriethoxysilane 100 100 50 100
100 20 100 100 20 100 90 20 5
gamma-Methacryloxypropyltrimethoxysilane 100 100 50 100 80 10 100
90 10 100 90 10 6 gamma-Mercaptopropyltrimethoxysilane 100 60 60
100 60 10 100 60 10 100 60 10 7 Vinyltriethoxysilane 90 50 30 90 50
20 90 20 5 50 10 10 8 Phenyltriethoxysilane 90 50 40 90 -- 10 10 10
5 30 5 5 9 n-Propyltrichlorosilane 100 100 40 60 50 20 40 10 5 20
10 5 10 Ethyltriethoxysilane 50 50 5 60 20 5 20 5 5 20 10 5 11
Control 10 -- -- 10 -- -- 5 -- -- 5 -- --
__________________________________________________________________________
The above data demonstrate the effectiveness of the silanes in
improving adhesion in the compositions of the invention. It may be
observed that silanes similar to those used in the prior art (see
Nos. 8 and 10) yield vastly inferior compositions.
EXAMPLE VI
Mastic compositions for coating steel pipe used in underground and
underwater pipeline installations were prepared. Components of the
mastic are sand (622 parts) having a gradation of 49.7% W of 8
.times. 16 mesh, 25.6% W of 16 .times. 30 mesh, 15.2% W of 30
.times. 50 mesh, 6.3% W of 50 .times. 100 mesh, 1.6% W of 100
.times. 200 mesh and 1.6% W of less than 200 mesh, limestone dust
(264 parts), fiberglass, 1.3 parts, and asphalt (58) parts) having
a softening point of 197.5.degree. F. and a penetration of 18 at
77.degree. F.
The sand and limestone are heated to not more than 450.degree. F.
The glass fiber, chopped to one-fourth inch filament lengths is
willowed and added to the aggregate. The aggregate and glass fiber
are mixed sufficiently to ensure thorough dispersion of the glass
fiber in the mass. The asphalt heated to not more than 425.degree.
F. is added to the mass and mixed to ensure complete dispersion in
the mass. The temperatures of the aggregate and asphalt are
controlled to yield a mastic mix having a temperature between
280.degree. and 400.degree. F. The mixture is formed into a
cylinder four inches in diameter and two-and-one-half inches tall.
The resilient modulus (M.sub.R) of the sample is determined dry.
See Schmidt, R. J., "A Practical Method of Measuring the Resilient
Modulus of Asphalt-Treated Mixes," Highway Research Record No. 404,
Highway Research Board, 1972.
The sample is saturated with water under vacuum and the resilient
modulus is determined again after 30 days' water immersion at room
temperature.
Samples in which both the sand and limestone or sand only were
pretreated to have a residue of 0.03% W of the silane of Example I
were also prepared and tested as described. The results are shown
in Table VI.
TABLE VI
__________________________________________________________________________
Resilient Modulus (M.sub.R) .times. 10.sup.5, psi Fiber.sup.2
Aggregate 60 Days Percent M.sub.R No. Fiber.sup.1 Treatment
Treatment Dry Saturated Retained After 60 Days
__________________________________________________________________________
1 415.sup.3 Silane -- 8.32 2.95 35 2 851 Silane -- 9.76 3.79 39 3
588-37 Starch -- 9.90 3.40 35 4 415 Silane Silane 6.16 3.89 63 5
851 Silane Silane 11.34 7.79 69 6 415 Silane Silane-sand 8.70 6.39
73 only 7 851 Silane " 11.13 6.77 61
__________________________________________________________________________
.sup.1 Available from Owens Corning .sup.2 Fiberglass is given a
surface treatment of a silane or starch to prevent scoring during
handling .sup.3 1.7 parts used instead of 1.3 parts
The above data demonstrate that the silane treatment of the
fiberglass has essentially no effect on the water resistance of the
mastic composition. However, silane treatment of the entire
aggregate or the sand only greatly increases the water resistance
of the mastic. These compositions contain only one-half the usual
amount of asphalt to exaggerate the effects of the water exposure.
Degradation of the mastics for field use would be much slower.
While the invention has been described in detail and with reference
to specific embodiments, it will be obvious other variations and
embodiments can be effected within the spirit and scope of the
appended claims.
* * * * *